1. Field of the Invention
The present invention relates to the personalization or decoration of generally cylindrical substrates, and more particularly, to the on-demand digital thermal printing and application of images thereto.
2. Background Information
The printing systems of interest print alphanumeric information, designs and or logos onto a variety of cylindrical objects, such as pens, pencils, cosmetic items, medical devices (e.g., syringe barrels), etc. Accordingly, these systems require that the curved exterior surface of the cylindrical object contact a printing mechanism at all points of printing.
In prior known systems, several methods are used to print on cylindrical substrates. These methods include silk screening, hot stamping and pad printing. Unfortunately, these printing methods require runs of several units to be economical since each of these techniques requires a dedicated printing tool such as a screen, die or cliche. The tools, which are unique to the particular information or design to be printed, add significant cost. In addition, the inks, dies and chemicals used with conventional processes are environmentally hazardous, which adds the additional cost of disposal.
Silk-screening for example involves the use of a stencil and inking apparatus. Typically, the cylindrical substrate is brought into rotational contact with the stencil while a squeegee or other device pushes ink through the opposite side of the stencil. While this method of printing produces an adequate image, each change in design requires a replacement stencil. Hot stamping cylindrical print systems produce high quality print by means of a curved heated die carrying a specified design. The heated die presses a pigmented or metalized foil against the outer surface of the cylindrical object such that print is formed on areas where the heated die contacts the foil. Any change in design similarly requires a replacement die.
It is therefore an object of the present invention to a method and system for producing and applying images to a generally cylindrical substrate that is adaptable for economically printing short runs of different images.
To accomplish the foregoing and other objects, features and advantages of the present invention we have provided a digitally-controlled thermal printing system that uses a digital print engine to generate and print selected images onto a cylindrical substrate using a thermal foil. Digital technology allows each applied image to be unique and printed on demand.
The invention includes a system and apparatus for rotationally supporting and advancing a cylindrical substrate and a supply of thermal foil in synchronous cooperation with a print strobe. In certain embodiments of the present invention the thermal foil is used to advance and rotate the cylindrical substrate being printed. In additional embodiments the thermal foil and substrate are synchronously independently advanced using a variety of advancement means.
The invention makes use of unique thermal foils designed for application by a digital print engine. Particularly, the thermal foils include a film carrier that resists distortion when subjected to the pressures and relatively high temperatures associated with the digital thermal printing process. More specifically, these thermal foils include a backcoating that comes into contact with the print head. The backcoating includes a lubricant that reduces the drag of a thermal print head, thus preventing the thermal foils from sticking to the thermal print head during printing.
The thermal foils used by the inventive system further include a top coat that resists distortion when subjected to the elevated temperatures (approaching 400 degrees F.) associated with the digital transfer process. The thermal foil preferably also includes a fast-acting yet aggressive thermally activated adhesive (size coat) that facilitates image transfer from the foil to a substrate.